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From |
David Airey <david.airey@vanderbilt.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: Covariates in ANOVAs |

Date |
Fri, 15 May 2009 07:38:35 -0500 |

. xi3 is not recommended for the following commands:

If Stata would just expand xi's capabilities, we could be happier. -Dave On May 14, 2009, at 10:48 PM, Joseph Coveney wrote:

Miss Gina Micke wrote:I would like to know how to control for an independent continuousvariable whenusing a repeated measures ANOVA. I have a 2x2 factorial designexperiment withmales and females in each of the treatment groups (T1 & T2) measuredat multiple"events", each subject assigned an "id". The subjects are alldifferent ages soI would like to be able to control for the effect of "age range".If I didn't have "age range" as a covariate my model would be asfollows:anova x T1 T2 sex T1*T2 T1*sex T2*sex T1*T2*sex/id|T1*event T2*eventT1*T2*eventsex*event sex*T1*event sex*T2*event T1*T2*sex*event, repeated(event)partialbse(id|T1*T2*sex)Do I use the ANCOVA and cont(age range) command? Is this output theeffects ofmy fixed factors taking into account the effect of age range? --------------------------------------------------------------------------------First, the command line text shown doesn't look at all like correctsyntax.Second, by the name of it, a variable called "age range" would becategoricaland so you would not be using the -continuous()- option for it in -anova-.Unless you have balanced data (equal representation of age rangeswithin eachfactorial cell, as well as equal sex-by-treatment group cell sizesmaintainedthroughout the observation period), try something like the followingto startwith: xi3 i.treatment_group*i.age_group*i.sex*i.observation_interval xtmixed response _I* || patient_id: , nolrtest variance remlYou'll need to install the user-written command, -xi3-, from SSC ifyou haven'talready. Joseph Coveney * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

* * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Covariates in ANOVAs***From:*Miss Gina Micke <gina.micke@uqconnect.edu.au>

**st: RE: Covariates in ANOVAs***From:*"Joseph Coveney" <jcoveney@bigplanet.com>

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